The present invention is related to folding knives that provide a safety lock feature to prevent unintended closure of the knife blade.
A folding "pocket" knife has a folding blade that is pivoted to a handle about a pin transverse to the length of the knife. The blade "tang" or base is typically curved about the pivot pin. An elongated bar spring on the handle rides against the tang surface to prevent or resist undesired movement of the blade between its open and closed positions.
Some folding knives have a safety lock feature which will prevent inadvertent folding of the blade from the open to the closed position. Blades that do not have this safety feature are a potential hazard. An unlocked blade can fold quickly to its closed position in response to forces applied in a direction substantially perpendicular to the folding pin. Such forces may be applied by the user making a forward thrusting or gouging motion with the knife. The blade will quickly move toward the closed position and might severely cut the user's hand.
Various mechanisms have been designed to securely lock folding knife blades in the open position. They are typically complex and add substantially to the cost of the knife. Further, the additional elements involved increase the chance of malfunction and early wear.
U.S. Pat. No. 1,258,150 to Schrade discloses a self-opening, locking and unlocking pocketknife. A button on the side of the handle is used to actuate a spring mechanism for opening the blade. The button is also movable longitudinally to bring a locking member into engagement with the tang of the blade, locking it into position. U.S. Pat. No. 400,987 to Wilzen and U.S. Pat. No. 2,530,236 to Erickson both disclose pocketknives with button locking and unlocking devices. The buttons are spring-actuated on the blade handles. Notches are formed in the blade tangs. Parts of the pins on the buttons include a shape complementary to the notches formed in the tangs. The tang notches and complementary button portions align with one another when the blades are in the open position. Movement of the buttons into engagement with the notches serves to lock the blades in the open position. Another axial part of each button is of reduced cross-section. When the buttons are pushed to bring the reduced portions into the tang notches the blades will release and can be closed.
U.S. Pat. No. 2,183,378 to Conklin shows a safety pushbutton knife. Here, the button is connected to a pivot lever (FIG. 2), one end of which is engaged with the button and the opposite end is engaged with a notch on the blade tang.
U.S. Pat. No. 2,304,601 to Schrade discloses another form of pocket knife having a slide operated detent mechanism for "locking" the blade in an open position.
Another presently available knife has a locking arrangement comprised of a spring release mechanism at a rearward end of the handle adjacent the blade spring bar. Actuation of the release causes pivotal movement of a dog from engagement with the locking spring. These mechanisms are somewhat simpler than the prior button arrangements but have drawbacks both in safety and in economics. The position of the release on the handle requires a haphazard grip to move the blade safely to the closed position. In addition the added elements and machining necessarily add to the cost of the knives.
It therefore becomes desirable to obtain some form of folding knife with a simple, uncomplicated and inexpensive locking mechanism for securely holding the blade in an open position. It is also desirable to have such a device on the knife blade that is situated for ease in operator control and safety.